This invention relates to an apparatus for preparing a woven fabric for seaming. More particularly, the present invention relates to a cutter for the cutting and removal of transverse yarns from a portion of a fabric to provide an area which is used in forming a seam. In most fabrics, the transverse yarns are weft yarns.
Many industrial devices require what is effectively a continuous length of woven fabric, for example the fabrics used in a papermaking machine to carry the paper web that is being made; in sequence these are a forming fabric, a press felt fabric and a dryer fabric. Each of these fabrics comprises at least one continuous fabric loop which circulates within each of the forming, press, and dryer sections of the papermaking machine. Although it is possible to weave a fabric for a small machine as a continuous loop, in many applications this is not necessary. Generally, the fabric is woven as a continuous run, cut to a desired length, and the thus formed ends seamed to provide the required loop of fabric.
A woven seam is preferred in forming fabrics, because it can provide a smooth, flat, join which does not alter significantly the drainage properties of the fabric. To create a woven seam, the transverse threads near to the edge of the two ends of the fabric are removed, to provide a fringe consisting of exposed longitudinal yarn ends. The two fringes are then overlayed, and the longitudinal yarns from one end are rewoven into the other end, as far as possible into the same yarn path thus preserving the fabric weave pattern. Alternatively, the exposed yarn ends are woven back into the same fabric end to provide loops, which are joined to each other by a pintle or by a spiral coil.
For some applications, a relatively narrow strip of woven fabric is converted into a loop using the spiral winding technique described by Best, in U.S. Pat. No. 5,268,076, by Rexfelt, in U.S. Pat. No. 5,360,656, and by Fekete, in U.S. Pat. No. 5,785,818. The spirally wound loop of fabric is flattened, and the two ends formed by the folding step are seamed together. A woven seam is not used, instead a length of warp is exposed at the fold line to provide pintle loops; the two ends are joined by interdigitating the pintle loops and inserting a pintle or a plastic spiral.
It is difficult and time consuming to prepare these fabrics for seaming. In the past, the longitudinal and transverse yarns, which are most often the warps and wefts, at the two ends of a length of fabric have been unravelled manually. This is a slow, labour intensive process which must be carried out with considerable care if the fabric adjoining the unravelled portions is not to be damaged. This is particularly true for the fabrics used in modern wide high speed papermaking machines, which can be over 10 meters wide.
It has been proposed to automate this process.
Kxc3x6pcke, in U.S. Pat. No. 4,736,499 describes a device in which vertically reciprocating needles pull sections of weft thread out of the plane of the fabric which are then cut out by a cutter, to provide a strip across the fabric in which a predetermined length of weft has been removed. A difficulty with the Kxc3x6pcke machine is that in one pass it can only remove as many weft threads as there are needles provided to pull them out of the plane of the fabric. If a longer length of warp has to be exposed to make the seam, then the machine has to traverse the width of the fabric more than once.
Kuster et al., in U.S. Pat. No. 6,014,797 describe s similar device in which a needle including a hook is used to pull a weft out of the plane of the fabric to be cut by a separate cutter. The machine then moves a preset distance to cut the next weft. A difficulty with the Kuster et al. machine is that it cannot move across the fabric to capture successive wefts which are not parallel to the line of the edge of the fabric. This creates problems when a Kuster et al. machine is used to prepare a spirally wound fabric for seaming, because the wefts in such fabrics are not parallel to the fabric edges.
A further problem common to both the Kxc3x6pcke and Kuster et al. machines is that a two part cutter unit is used. The wefts are physically pulled out of the plane of the fabric by a hooked needle and a separate cutter severs the deflected length of weft. This complicates the cutting process, because the friction inherent in a heat set weave may not be sufficient to resist the lateral force applied to the fabric by the needle, so that the fabric adjoining the area in which the seam is to be made can become distorted. This is not desirable.
This invention seeks to overcome these difficulties, and to provide an apparatus for preparing a fabric for seaming in which the methods disclosed by Kxc3x6pcke and Kuster et al. to move the cutter unit relative to the fabric are utilised, but a different integrated cutter is used. In the following description it is assumed that, as described by both Kxc3x6pcke and Kuster et al., the fabric area which is being prepared for seaming is carried on suitable surface in a substantially horizontal plane with the cutter unit located beneath the fabric; other orientations could be used if desired.
The integrated cutter of this invention includes a hooked needle which moves in a guide bushing, with the guide bushing top end located very close to the plane defined by the lower surface of the fabric. This integrated cutter can be used both to form an edge fringe for a woven seam in a conventional fabric as described by Kuster et al., to form an area of exposed warp yarns to provide pintle loops to be joined by a pintle or a plastic spiral as described by Kxc3x6pcke, and to prepare the ends of a flattened loop of spiral wound fabric for seaming.
In the integrated cutter of this invention, a hooked needle oscillates vertically into and.out of the fabric in a guide bushing supported by a carrier beneath the fabric. The needle oscillates between a retracted position where the head of the needle is not exposed and an extended position in which the needle penetrates the fabric. The upper end of the guide bushing is more or less in contact with the lower surface of the fabric. The needle head is shaped so that when it moves upwardly it pushes between a pair of yarns in one direction, for example warp yarns, with minimal, if any, damage to either of them, until the hook is above a yarn in the other direction, for example a weft yarn. The needle hook includes a transverse groove shaped so that when it moves downwardly it captures this yarn. The needle is a close fit within the guide bushing, to ensure cooperation between cutting edges at the lateral ends of the transverse groove and at the periphery of the hole at the top end of the guide bushing around the needle. Consequently, a short length of the trapped yarn corresponding approximately to the width of the groove in the needle is severed cleanly as the cooperating cutting edges at each side of the hook and at the top end of the guide bushing pass each other. When the needle has moved downwardly to be within the guide bushing, so that the needle head is not exposed, the carrier moves the device laterally a preset distance, and the cycle is repeated to cut another section of yarn. During the cutting process, the fabric is held more or less flat on the supporting surface by a relatively light shuttle, which moves with the carrier supporting the guide bushing. It can thus be seen that the yarns are cut into quite short pieces which fall away beneath the fabric and are trapped, for example by a vacuum system. Further, since the integrated cutter of this invention does not rely on friction within the fabric to hold the wefts as they are cut, distortion of the adjacent area of the fabric is minimised. Additionally, the integrated cutter of this invention can be moved either parallel to, or orthogonal to, the edge of the fabric.
Thus in a broad embodiment this invention seeks to provide an integrated cutter device, for an apparatus for preparing for seaming a selected area of a woven fabric, which fabric has a lower surface adjacent the apparatus and an upper surface remote from the apparatus, and which includes longitudinal and transverse yarns in the weave pattern, the integrated cutter device comprising in combination:
a needle including a shank, a head and a hook located adjacent to the head;
a guide bushing having an axial aperture which is constructed and arranged to be a close fit on the needle shank and which has a first end face;
a shuttle means located on the upper surface of the fabric including a space to receive the head of the needle;
a first carrier means to support the needle and the guide bushing with the first end face of the guide bushing close to the lower surface of the preselected area of fabric;
a second carrier means to locate the shuttle with the space over the guide bushing aperture;
a means to oscillate the needle in the guide bushing between a preselected retracted position and a preselected extended position; and
means to move both of the first and the second carrier means together a preselected distance relative to the selected area of fabric, wherein:
(a) the head of the needle is constructed and arranged to be pushed between a pair of yarns in a first direction with minimal damage to either of them;
(b) the hook comprises a shaped groove across the shank of the needle constructed and arranged to trap within the groove one yarn in a second direction in the fabric;
(c) the first and second directions are substantially orthogonal to each other, and one of them corresponds to the direction of the longitudinal yarns;
(d) the shaped groove is formed with a pair of first cutting edges at each of its ends;
(e) the guide bushing first end face is formed with a pair of second cutting edges which cooperate with the pair of first cutting edges;
(f) the needle retracted position is preselected to locate the head of the needle within the guide bushing axial aperture close to the first end face of the guide bushing;
(g) the needle extended position is preselected to locate the needle hook above the upper surface of the fabric; and
(h) the preselected distance through which the carrier means are moved together corresponds to a distance NX, in which N is an integral number and X is chosen from the group consisting of the linear spacing between adjacent longitudinal yarns and the linear spacing between adjacent transverse yarns.
Preferably, the guide bushing first end face comprises a replaceable section of harder material to provide the pair of second cutting edges.
Preferably, the needle head has a tapering pointed shape.
Preferably, the needle shank and head have a triangular cross section, the hook groove is located substantially parallel to one of the faces of the triangle and the hook opening is toward the opposite apex of the triangle. More preferably, the needle shank and head have an isosceles triangular cross section, the hook groove is located substantially parallel to the shortest face of the triangle, and the hook opening is toward the opposite apex of the triangle. Most preferably, the needle shank and head have an isosceles triangular cross section, the hook groove is located substantially parallel to a face of the triangle, the hook opening is toward the opposite apex of the triangle and the needle head has a tetrahedral shape.
Preferably, the means to oscillate the needle between the retracted and extended positions comprises a linear motion device. More preferably, the means to oscillate the needle comprises a linear motion device chosen from the group consisting of a solenoid device, a cam device, and an air cylinder. Preferably, the linear motion device comprises an air cylinder. More preferably, the linear motion device comprises a double acting air cylinder.
Preferably, the means to move both of the first and the second carrier means together a preselected distance relative to the selected area of fabric comprises an intermittently actuated lead screw device.